There has been a need for an effective snubber brake for use with suspended, swinging bodies such as grapples suspended from the rear sections of logging skidders and like vehicles. Grapple heads are in wide use in the logging industry and are normally suspended from an arch boom on the rear of the vehicle by means of a universal pivot joint which allows the grapple to be rotated and swung in all directions. Because logging vehicles operate over extremely rough terrain, grapple heads can, without proper restraint, swing around violently and possibly strike the vehicle to which it is connected, and/or damage itself and the vehicle as well. Accordingly, some form of restraint or braking means is needed to keep movement of the grapple head in check.
Snubber brakes of various types for grapple heads have been known for some time. Conventionally, a snubber brake is constantly applied to the moveable members of the apparatus. The tension that the brake is set to is crucial because too much tension will not allow the grapple head to swing properly to the ground but too little tension will result in the grapple head swinging excessively.
Several of the serious problems with conventional brake arrangements is that they are usually complicated and expensive to manufacture and they often require special equipment for adjustment and repair. More often than not, a grapple head must be removed from the arch boom on a logging vehicle to make the brake mechanisms accessible to the operator. This results in expensive down time. Brake maintenance can also be dangerous because removing the mechanism that connects a grapple to a boom or snubber link can sometimes result in the grapple head falling and causing severe injury to an operator repairing the brake.
A grapple head can weigh anywhere from 800 to 3000 pounds so the result of such a piece of equipment falling can be of serious concern indeed for an operator. In the rugged environment logging skidders or like vehicles are working, there is normally no crane available to hook a grapple nor a boom to support the head. A repair crew or operator must jury-rig some form of prop or support system using unsafe methods.
Examples of some prior art in this field may be found in Canadian Patents 1,229,108 issued Nov. 10, 1987; 894,632 issued Mar. 7, 1972; Canadian Laid-open Patent Application 2,052,616 published Apr. 4, 1992 and the following United States patents:
______________________________________ 4,572,567 February 25, 1986 3,592,503 July 13, 1971 4,717,191 January 5, 1988 4,715,641 December 29, 1987. ______________________________________